[llvm] [InstCombine] Queue Xor for deletion after replacing its uses in freelyInvertAllUsersOf. (PR #72445)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Craig Topper (topperc)

<details>
<summary>Changes</summary>

Fixes #<!-- -->72433

---
Full diff: https://github.com/llvm/llvm-project/pull/72445.diff


2 Files Affected:

- (modified) llvm/lib/Transforms/InstCombine/InstructionCombining.cpp (+2) 
- (added) llvm/test/Transforms/InstCombine/pr72433.ll (+27) 


``````````diff
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 16de4e3ffe1f51a..463a7b5bb1bb588 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -1185,6 +1185,8 @@ void InstCombinerImpl::freelyInvertAllUsersOf(Value *I, Value *IgnoredUser) {
       break;
     case Instruction::Xor:
       replaceInstUsesWith(cast<Instruction>(*U), I);
+      // Add to worklist for DCE.
+      addToWorklist(cast<Instruction>(U));
       break;
     default:
       llvm_unreachable("Got unexpected user - out of sync with "
diff --git a/llvm/test/Transforms/InstCombine/pr72433.ll b/llvm/test/Transforms/InstCombine/pr72433.ll
new file mode 100644
index 000000000000000..ec3fcfcfea46fcf
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/pr72433.ll
@@ -0,0 +1,27 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
+; RUN: opt -passes=instcombine -S < %s | FileCheck %s
+
+define i32 @widget(i32 %arg, i32 %arg1) {
+; CHECK-LABEL: define i32 @widget(
+; CHECK-SAME: i32 [[ARG:%.*]], i32 [[ARG1:%.*]]) {
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    [[ICMP:%.*]] = icmp ne i32 [[ARG]], 0
+; CHECK-NEXT:    [[TMP0:%.*]] = zext i1 [[ICMP]] to i32
+; CHECK-NEXT:    [[MUL:%.*]] = shl nuw nsw i32 20, [[TMP0]]
+; CHECK-NEXT:    [[XOR:%.*]] = zext i1 [[ICMP]] to i32
+; CHECK-NEXT:    [[ADD9:%.*]] = or i32 [[MUL]], [[XOR]]
+; CHECK-NEXT:    [[TMP1:%.*]] = zext i1 [[ICMP]] to i32
+; CHECK-NEXT:    [[MUL2:%.*]] = shl nuw nsw i32 [[ADD9]], [[TMP1]]
+; CHECK-NEXT:    ret i32 [[MUL2]]
+;
+bb:
+  %icmp = icmp eq i32 %arg, 0
+  %zext = zext i1 %icmp to i32
+  %sub = sub i32 2, %zext
+  %mul = mul i32 20, %sub
+  %zext8 = zext i1 %icmp to i32
+  %xor = xor i32 %zext8, 1
+  %add9 = add i32 %mul, %xor
+  %mul2 = mul i32 %add9, %sub
+  ret i32 %mul2
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/72445